1. Field of the Invention
The present invention relates to a semiconductor device including an oxide semiconductor and a manufacturing method thereof.
In this specification, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics, and an electrooptic device, a semiconductor circuit, and an electronic device are all semiconductor devices.
2. Description of the Related Art
Solid-state image sensing devices are broadly classified into charge-transfer-type solid-state image sensing devices typified by CCD image sensors and amplification type solid-state image sensing devices typified by CMOS image sensors.
A two-dimensional solid-state image sensing device in which pixels each including a photoelectric conversion element such as a photodiode and a means for extracting photocharge generated in the photoelectric conversion element to an output signal line are arranged in a matrix has been widely used. For example, a two-dimensional solid-state image sensing device is mounted on a camera-equipped mobile phone or a portable information terminal such as a PDA.
A technique for manufacturing a transistor or the like by using an oxide semiconductor layer for a channel formation region and applying it has been attracting attention. Examples of such a transistor include a transistor including zinc oxide (ZnO) in an oxide semiconductor layer and a transistor including InGaO3(ZnO)m in an oxide semiconductor layer.
Patent Document 1 discloses a structure in which a pixel in a display device is provided with two different elements, i.e., a transistor including an oxide semiconductor layer and a photodiode including amorphous silicon in a photoelectric conversion layer.